Erythropoietin (Epo) is a hormone produced by the kidneys and/or liver which determines the number of red blood cells produced. Recently, the nucleotide sequence of a cDNA which encodes this glycoprotein hormone has been determined. From this and from the amino acid sequence of tryptic peptides the complete amino acid sequence of the protein has been deduced. The goal of this project is to synthesize peptide analogs of various regions of the Epo amino acid sequence, and to use these peptide analogs as antigens for the production of antisera which can be used to develop a RIA for Epo. An immunoassay developed by this procedure would not require pure erythropoietin, but would only require the production of a pure peptide analog, which can by synthesized very economically on a large scale. The RIA which is to be developed during this project will be commercially available to physicians, clinical laboratories, and researchers for the diagnosis of patients with erythropoietic disorders and for monitoring the treatment of patients with various kidney disorders.